Final answer:
Multiple genetic changes occur in a cell lineage before cancer develops, typically involving mutations in many genes, including oncogenes and tumor suppressor genes.
Step-by-step explanation:
In most cases, multiple genetic changes occur in a cell lineage before cancer develops. These changes can range from small mutations affecting a single DNA nucleotide to gain or loss of entire chromosomes. Typically, changes in many genes, including oncogenes and tumor suppressor genes, are required to transform a normal cell into a cancer cell.